The present invention is an improved process for the synthesis of 1-phenylvinyl-1-phosphonic acid (PVPA), which can be polymerized to higher molecular weight species or processed with further polymerizable compounds in the manufacture of copolymers. Some representative references which describe how this well-known compound can be formed include the following: Conant et al. J. Amer. Chem. Soc. 44, 2530-2536 (1922), which shows the use of acetophenone, phosphorus trichloride, and glacial acetic acid as reagents; and U.S. Pat. No. 4,529,559, which shows the reaction of acetophenone, phosphorus trichloride, and water in Example 5 under heating conditions of up to 150.degree. C. The temperature conditions used in the previously mentioned patent were used to remove residual acetophenone from the reaction mixture but they can lead to a lessened product yield due to the formation of dimeric and oligomeric by-products.